/*
 * ClassInstantiator.java December 2009
 *
 * Copyright (C) 2009, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

import java.util.ArrayList;
import java.util.List;

import wx.xml.simpleframework.xml.stream.Node;

/**
 * The <code>ClassInstantiator</code> is used for instantiating
 * objects using either the default no argument constructor or one
 * that takes deserialized values as parameters. This also exposes
 * the parameters and constructors used to instantiate the object.
 *
 * @author Niall Gallagher
 */
class ClassInstantiator implements Instantiator {

    /**
     * This contains a list of all the creators for the class.
     */
    private final List<Creator> creators;

    /**
     * This is used to acquire a parameter by the parameter name.
     */
    private final ParameterMap registry;

    /**
     * This represents the default no argument constructor used.
     */
    private final Creator primary;

    /**
     * This contains the details for the class to instantiate.
     */
    private final Detail detail;

    /**
     * Constructor for the <code>ClassCreator</code> object. This is
     * used to create an object that contains all information that
     * relates to the construction of an instance.
     *
     * @param creators contains the list of all constructors available
     * @param primary  this is the default no argument constructor
     * @param registry contains all parameters for the constructors
     * @param detail   contains the details for the instantiated class
     */
    public ClassInstantiator(List<Creator> creators, Creator primary, ParameterMap registry, Detail detail) {
        this.creators = creators;
        this.registry = registry;
        this.primary = primary;
        this.detail = detail;
    }

    /**
     * This is used to determine if this <code>Creator</code> has a
     * default constructor. If the class does contain a no argument
     * constructor then this will return true.
     *
     * @return true if the class has a default constructor
     */
    @Override
    public boolean isDefault() {
        int count = creators.size();

        if (count <= 1) {
            return primary != null;
        }
        return false;
    }

    /**
     * This is used to instantiate the object using the default no
     * argument constructor. If for some reason the object can not be
     * instantiated then this will throw an exception with the reason.
     *
     * @return this returns the object that has been instantiated
     */
    @Override
    public Object getInstance() throws Exception {
        return primary.getInstance();
    }

    /**
     * This is used to instantiate the object using a constructor that
     * takes deserialized objects as arguments. The object that have
     * been deserialized can be taken from the <code>Criteria</code>
     * object which contains the deserialized values.
     *
     * @param criteria this contains the criteria to be used
     * @return this returns the object that has been instantiated
     */
    @Override
    public Object getInstance(Criteria criteria, Node node) throws Exception {
        Creator creator = getCreator(criteria);

        if (creator == null) {
            throw new PersistenceException(this, "Constructor not matched for %s at:%s (%s)", detail, node.getLocation().debugDescription(), node.debugDescription());
        }
        return creator.getInstance(criteria);
    }

    /**
     * This is used to acquire an <code>Instantiator</code> which is used
     * to instantiate the object. If there is no match for the instantiator
     * then the default constructor is provided.
     *
     * @param criteria this contains the criteria to be used for this
     * @return this returns the instantiator that has been matched
     */
    private Creator getCreator(Criteria criteria) throws Exception {
        Creator result = primary;
        double  max    = 0.0;

        for (Creator instantiator : creators) {
            double score = instantiator.getScore(criteria);

            if (score > max) {
                result = instantiator;
                max = score;
            }
        }
        return result;
    }

    /**
     * This is used to acquire the named <code>Parameter</code> from
     * the creator. A parameter is taken from the constructor which
     * contains annotations for each object that is required. These
     * parameters must have a matching field or method.
     *
     * @param name this is the name of the parameter to be acquired
     * @return this returns the named parameter for the creator
     */
    @Override
    public Parameter getParameter(String name) {
        return registry.get(name);
    }

    /**
     * This is used to acquire all parameters annotated for the class
     * schema. Providing all parameters ensures that they can be
     * validated against the annotated methods and fields to ensure
     * that each parameter is valid and has a corresponding match.
     *
     * @return this returns the parameters declared in the schema
     */
    @Override
    public List<Parameter> getParameters() {
        return registry.getAll();
    }

    /**
     * This is used to acquire all of the <code>Instantiator</code>
     * objects used to create an instance of the object. Each represents
     * a constructor and contains the parameters to the constructor.
     * This is primarily used to validate each constructor against the
     * fields and methods annotated to ensure they are compatible.
     *
     * @return this returns a list of instantiators for the creator
     */
    @Override
    public List<Creator> getCreators() {
        return new ArrayList<Creator>(creators);
    }

    /**
     * This is used to acquire a description of the creator. This is
     * useful when debugging an issue as it allows a representation
     * of the instance to be viewed with the class it represents.
     *
     * @return this returns a visible description of the creator
     */
    public String toString() {
        return String.format("creator for %s", detail);
    }
}